1. Field of the Invention
The present invention relates to an imaging apparatus and an imaging method which conduct fixed length compression. More particularly, the invention relates to an imaging apparatus and an imaging method, which reduce the number of processes for compressing a main image to a fixed length.
2. Description of the Related Art
For a still image compression format in an image processing apparatus such as a digital camera, JPEG (Joint Photographic Experts Group) has been adopted as a standard. In an image cording apparatus having a limitation for recording capacity such as a digital camera, there has been a demand for an image size to be a fixed length in order to indicate remaining number of imageable sheets for a user. Therefore, it has been becoming common that fixed length cording is carried out by JPEG format of a variable length cording method. On the other hand, when an image is created by a digital camera, it is common that as well as a main image, a reduced image for display is created in order to simply distinguish contents of a file, and it is usual that the main image and the reduced image for display are created from the same data.
As the above imaging apparatus which conducts a conventional fixed length compression, there are image processing method and image processing apparatus disclosed in JP-A-H09-294265 which were proposed by the present applicant. This apparatus converts image data into frequency transform coefficient by using discrete cosine transform coefficient, and quantizes by using quantization coefficient denoting weight of the quantization of the converted frequency transform coefficient. The apparatus encodes the quantized data, and detects a data coding amount coded at each predetermined time interval during execution of the coding processing of the quantized data by the coding means, and then revises the quantization coefficient based on the detected code amount during the execution of the coding processing.
However, in the above invention, a method to decrease the amount of time for a fixed length is considered separately from the creation of the reduced image for display. Since an image size depends upon contents of an image, the image size is determined after the image is actually compressed. Accordingly, when the image is compressed, and if the compressed image is not fitted to a target size, a compression size was required to be changed.